Compact high voltage RF generator using a self-resonant inductor

ABSTRACT

RF generators including active devices driving series resonant circuits are described. The series resonant circuits include a self-resonant dual inductor. The RF generators can be used to drive capacitive loads.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to radio frequency (RF)generators and more particularly to RF generator circuits using aninductor.

RF generators produce high frequency signals useful for manyapplications, for example, for use in ion mobility spectrometers (IMS)and field asymmetric ion mobility spectrometers (FAIMS) or differentialmobility spectrometers (DMS). In a spectrometer, molecules in a sampleof air are ionized and are admitted into a drive region of a cell. Theionized molecules drift to the opposite end of the cell at a speeddependent on the size of the ion to a collector, which causes a currentpulse in the collector. The current into the collector is converted to avoltage and amplified. By measuring the time of flight along the cell itis possible to identify the ion.

The subject matter discussed in this background of the invention sectionshould not be assumed to be prior art merely as a result of its mentionin the background of the invention section. Similarly, a problemmentioned in the background of the invention section or associated withthe subject matter of the background of the invention section should notbe assumed to have been previously recognized in the prior art. Thesubject matter in the background of the invention section merelyrepresents different approaches, which in and of themselves may also beinventions.

SUMMARY OF THE INVENTION

RF generator circuits including a series resonant circuit are described.In one embodiment, an RF generator circuit includes an active devicedriving the series resonant circuit that includes a bifilar toroidaldual inductor. The RF generator circuits may be used to produce a highload voltage at a high frequency to drive a capacitive load.

In one aspect, an embodiment of a circuit including a dual inductor isprovided. The dual inductor includes a toroidal core. The circuitincludes a winding on the toroidal core. The winding includes an inputand an output. The circuit also includes another winding on the toroidalcore. The another winding includes an input and an output. The circuitalso includes a capacitor electrically coupled to the input of the onewinding in parallel with the one winding. The circuit also includesanother capacitor electrically coupled to the input of the anotherwinding in parallel with the another winding. The outputs of thewindings are configured to electrically couple to a capacitive load.

In another aspect, an embodiment of an RF generator circuit including apower supply, an active device configured to output a signal, a dualinductor including a pair of windings wound on a toroidal core, and acapacitor is provided. The capacitor is electrically coupled with one ofthe windings of the dual inductor. The power supply and the activedevice are electrically coupled with the capacitor and the one of thewindings of the dual inductor. The dual inductor is configured toprovide a voltage step up of the signal of the active device.

Another embodiment of the invention relates to a method of generating asignal. The method includes providing a drive signal to an activedevice. The method also includes providing a power supply. The methodalso includes providing a circuit including a bifilar toroidal dualinductor and a capacitor electrically coupled in parallel with at leastone of the windings of the bifilar toroidal dual inductor. The activedevice and the power supply are electrically coupled to the circuit. Themethod also includes driving a capacitive load electrically coupled tothe circuit in series with the bifilar toroidal dual inductor.

This Summary of the Invention is provided to introduce a selection ofconcepts in a simplified form that are further described below in theDetailed Description. This Summary of the Invention is not intended toidentify key features or essential features of the claimed subjectmatter, nor is it intended to be used to limit the scope of the claimedsubject matter.

DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentify the figure in which the reference number first appears. The useof the same reference number in different instances in the descriptionand the figures may indicate similar or identical items.

FIG. 1 is a schematic illustration of a self-resonant dual inductor inaccordance with an embodiment of this disclosure;

FIG. 2 is a schematic illustration of a self-resonant dual inductor in aseries resonant circuit in accordance with an embodiment of thisdisclosure;

FIG. 3 is a schematic illustration of an embodiment of an RF generatorcircuit including an embodiment of a series resonant circuit with aself-resonant dual inductor in accordance with an embodiment of thisdisclosure;

FIG. 4 is a schematic illustration of another embodiment of an RFgenerator circuit including an embodiment of a series resonant circuitwith a self-resonant dual inductor in accordance with an embodiment ofthis disclosure; and

FIG. 5 is a schematic illustration of another embodiment of an RFgenerator circuit including an embodiment of a series resonant circuitwith a self-resonant dual inductor in accordance with an embodiment ofthis disclosure.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

Prior to turning to the figures, in one embodiment, an RF generatorusing an active device to drive a series resonant circuit including aself-resonant dual inductor is provided. In one embodiment, the RFgenerator produces two antiphase outputs at a higher voltage than asupply voltage of the RF generator at a frequency of at least oneMegahertz (MHz). Such outputs may be used to drive a capacitive load. Anembodiment of a self-resonant dual inductor is first described.

A self-resonant dual inductor, illustrated as a bifilar toroidal dualinductor 110 in FIG. 1 is provided. The bifilar toroidal dual inductor110 includes a generally toroid-shaped core 112. In one embodiment, thecore 112 is a low permeability magnetic core (e.g., formed from ironpowder, ferrite, or other suitable materials). Particularly, forexample, in one embodiment the core 112 is formed from T 80-6 ironpowder.

The core 112 is wrapped with a pair of windings 114 and 116. Thewindings 114 and 116 are insulated conductors. In one embodiment thematerial insulating the conductors has low RF loss and high breakdownvoltage characteristics, such as, for example, polytetrafluoroethylene(PTFE), or other suitable materials. The windings 114 and 116 arecoupled. The winding 114 provides an input 118 and an output 120.Likewise, the winding 116 provides an input 122 and an output 124.Embodiments of a bifilar toroidal dual inductor 110 provide a lowradiated magnetic field and, in some embodiments, a smaller size than anair-gap inductor. Additionally, in some embodiments, the bifilar windingconfiguration provides close coupling between windings and simpleconstruction. In one embodiment, the core 112 is not a split core (i.e.,does not have an air gap).

Such a bifilar toroidal dual inductor 110 may be used in variouscircuits. FIG. 2 illustrates a series resonant circuit 248 including aself-resonant dual inductor, such as the bifilar toroidal dual inductor210. One input 203 to the circuit 248 is electrically coupled with acapacitor 240 and the input 218 of the winding 214 of the bifilartoroidal dual inductor 210. The capacitor 240 is also electricallycoupled to ground. Another input 205 to the circuit 248 is electricallycoupled with another capacitor 242 and the input 222 of the winding 216of the bifilar toroidal dual inductor 210. The capacitor 242 is alsoelectrically coupled to ground. The output 220 of the winding 214 iselectrically coupled to a capacitor 244. The capacitor 244 is alsoelectrically coupled to ground. The output 224 of the winding 216 iselectrically coupled to a capacitor 246. The capacitor 246 is alsoelectrically coupled to ground.

Two inputs, with phases shifted from one another, may be applied to theinputs 203 and 205 of the series resonant circuit 248. The inductors ofthe bifilar toroidal dual inductor 210 are coupled, and the bifilartoroidal dual inductor 210 is a self-resonant dual inductor thatproduces two antiphase outputs. As illustrated in FIGS. 1 and 2, thebifilar toroidal inductor 310 is configured such that current flowthrough the windings 214 and 216 is in opposite directions. Theinter-winding capacitance of the bifilar toroidal dual inductor 210provides series resonance.

FIG. 3 is a schematic illustration of an embodiment an RF generatorcircuit 325 including a self-resonant dual inductor, illustrated as abifilar toroidal dual inductor 310. A power supply, illustrated as a lowvoltage DC power supply 326 in FIG. 3, is provided. The DC power supply326 is electrically coupled with a transformer 328. The transformer 328has two outputs 330 and 332. The transformer 328 produces two outputsthat are out of phase with one another at the outputs 330 and 332.

An active device, illustrated as a transistor 334, is also provided.While the transistor 334 is illustrated as an NMOS field effecttransistor in FIG. 3, in other embodiments other suitable transistors(e.g., PMOS FET's, JFET's, BJT's, etc.) are used. Additionally, anyother suitable active device may be used. The transistor 334 receives adrive signal at an input 336. The source of the transistor 334 iselectrically coupled to ground.

The output 338 of the transistor 334, in the illustrated embodiment thedrain of the transistor 334, and the first output 330 of the transformer328 are electrically coupled with the input 318 of the winding 314 ofthe bifilar toroidal dual inductor 310 and to the first capacitor 340.The first capacitor 340 is electrically coupled in parallel with thewinding 314 and is also electrically coupled to ground.

The second output 332 of the transformer 328 is electrically coupledwith the second capacitor 342 and the input 322 of the winding 316 ofthe bilfilar toroidal inductor 310. The second capacitor 342 iselectrically coupled in parallel with the winding 316 and is alsoelectrically coupled to ground.

The inductors of the bifilar toroidal dual inductor 310 are closelycoupled. The bifilar toroidal dual inductor 310 is a self-resonant dualinductor that produces two antiphase outputs. As illustrated in FIG. 3,the bifilar toroidal inductor 310 is configured such that current flowthrough the windings 314 and 316 is in opposite directions. The outputs320 and 324 may be used to drive a capacitive load, illustrated in FIG.3 (along with any stray capacitance in the dual inductor) as capacitors344 and 346.

The circuit of FIG. 3 is driven such that the bifilar toroidal dualinductor 310 resonates with a load capacitance, illustrated in FIG. 3(along with any stray capacitance in the dual inductor) as capacitors344 and 346. The series resonant circuit 348 is driven at its resonantfrequency to provide a voltage step up, such that outputs 320 and 324will be at a higher voltage than the inputs 318 and 322. With a highfrequency signal and the bifilar toroidal inductor 310 resonating withthe load capacitance 344 and 346, low power may be used to produce thehigher voltage at the high frequency at the high voltage outputs 320 and324. Thus, an impedance matching series resonant circuit 348 is providedfor low power, high frequency voltage step up. The bifilar toroidal dualinductor 310 is configured such that the interwinding capacitanceprovides a series resonance and a large voltage step-up.

In one embodiment, a bifilar toroidal dual inductor with a T 80-6 ironpower core is provided. The core has a 20 millimeter outside diameterand is 6 millimeters thick. The core is would with two windings, eachwith 35 turns. When the core is driven at 8 MHz with a supply voltage of30 V, a differential output of 3 kV peak-to-peak is achieved.

Voltage step up is dependent on the quality factor (“Q”) of theimpedance matching series resonant circuit 348. Both the quality factorand the resonant frequency of the series resonant circuit 348 may varybased on multiple different factors (e.g., temperature, componentdesign, etc.). Feedback, e.g., through use of, for example, a feedbackdevice, allows for regulation and stabilization of the output voltage ofthe network 348.

In one embodiment, a feedback device, illustrated as a small feedbackwinding 350 (e.g., 1 turn) wound to the bifilar toroidal dual inductor310, is provided. The feedback winding 350 is electrically coupled withthe input 336 of the active device 334. Thus, the RF generator circuit325 will be self-oscillating, with the active device continuing to drivethe series resonant circuit 348 at its resonant frequency. This providesfor an efficient RF generator circuit 325.

FIG. 4 is a schematic illustration of another embodiment of an RFgenerator circuit 425 including a self-resonant dual inductorillustrated as a bifilar toroidal dual inductor 410. A power supply,illustrated as a low voltage DC power supply 426 in FIG. 4, is provided.The DC power supply 426 is electrically fed through an inductor 452 withan output 454.

An active device, illustrated as a transistor 434 in FIG. 4, is alsoprovided. The transistor 434 receives a drive signal at its input 436.The source of the transistor 434 is electrically coupled to ground. Theoutput 438 of the transistor 434, in the illustrated embodiment thedrain of the NMOS field effect transistor, is electrically coupled inseries with a diode 456.

The diode 456 and the output 454 of the inductor 452 are electricallycoupled to the input 418 of the winding 414 of the bifilar toroidal dualinductor 410 and to a first capacitor 440. The first capacitor 440 iselectrically coupled in parallel with the winding 414 and is alsoelectrically coupled to ground. The input 422 of the winding 416 of thebifilar toroidal dual inductor 410 is electrically coupled to ground.

The outputs 420 and 424 are configured to be coupled in series with anddrive a capacitive load. The capacitive load (along with straycapacitance of the bifilar toroidal dual inductor 410) is schematicallyrepresented as load capacitors 444 and 446, which are coupled to theoutput 420 and the output 424 respectively.

The circuit of FIG. 4 is driven such that the bifilar toroidal dualinductor 410 resonates with the load capacitance 444 and 446 (along withany stray capacitance in the bifilar toroidal dual inductor 410). With ahigh frequency signal and the bifilar toroidal inductor 410 resonatingwith the load capacitance 444 and 446, low supply power is used toproduce the higher voltage at the high frequency at the outputs 420 and424 of the bifilar toroidal dual inductor 410. Thus, an impedancematching series resonant circuit 448 provides low power, high frequencyvoltage step up. The bifilar toroidal inductor 410 is configured suchthat the interwinding capacitance provides a series resonance and alarge voltage step-up.

In one embodiment, a feedback device, illustrated as a small feedbackwinding 450 (e.g., 1 turn) would to the bifilar toroidal dual inductor410, is provided. The feedback winding 450 is electrically coupled withthe active device 434. Thus, the RF generator circuit 425 will beself-oscillating and may be driven at the resonant frequency. Thisprovides for an efficient RF generator circuit 425.

In one embodiment, the diode 456 prevents the parasitic body diode ofthe NMOS field effect transistor from clamping and limiting the initialvoltage swing which drives the series resonant circuit 448 including thebifilar toroidal dual inductor 410. Additionally, the diode 456 allowsthe voltage applied to the series resonant circuit 448 to swingnegative, giving the series resonant circuit 448 a greater output.

FIG. 5 illustrates another embodiment of an RF generator circuit 525including a self-resonant dual inductor illustrated as a bifilartoroidal dual inductor 510. A power supply, illustrated as a low voltageDC power supply 526 in FIG. 5, is provided. The DC power supply 526 iselectrically coupled to a transformer 558. The transformer 558 includestwo outputs 560 and 562.

Two active devices, illustrated as transistors 534 and 564 in FIG. 5,are also provided. The transistor 534 receives a drive signal at itsinput 536. The source of the transistor 534 is electrically coupled toground. The output 538 of the transistor 534 and the output 560 of thetransformer 560 are electrically coupled to a first capacitor 540 and tothe input 518 of the winding 514 of the bifilar toroidal dual inductor510. The first capacitor 540 is electrically coupled in parallel withthe winding 514 and is also electrically coupled to ground.

The transistor 564 also receives a drive signal at its input 566. Thesource of the transistor 564 is electrically coupled to ground. Theoutput 568 of the transistor 564 and the output 562 of the transformer558 are electrically coupled to a second capacitor 542 and to the input522 of the winding 516 of the bifilar toroidal dual inductor 510. Thesecond capacitor 542 is electrically coupled in parallel with thewinding 516 and is also electrically coupled to ground.

The outputs 520 and 524 of the windings 514 and 516 are configured to becoupled in series with and drive a capacitive load. The capacitive load(along with stray capacitance of the bifilar toroidal dual inductor 510)is schematically represented as load capacitors 544 and 546, which arecoupled to the output 420 and the output 424 respectively.

The circuit of FIG. 5 is driven such that the bifilar toroidal dualinductor 510 resonates with the load capacitance 544 and 546 (along withany stray capacitance in the bifilar toroidal dual inductor 510). With ahigh frequency signal and the bifilar toroidal inductor 510 resonatingwith the load capacitance 544 and 546, low supply power is used toproduce the higher voltage at the high frequency at the outputs 520 and524 of the bifilar toroidal dual inductor 510. Thus, an impedancematching series resonant circuit 548 provides low power, high frequencyvoltage step up. The bifilar toroidal inductor 510 is configured suchthat the interwinding capacitance provides a series resonance and alarge voltage step-up.

Some applications may require a high frequency, high voltage waveform,such as those produced by embodiments of RF generator circuits asdescribed above. For example, ion modifiers, such as those described inU.S. Patent Application Publication No. 2011/0300638, assigned to theassignee of the present application and incorporated herein by referencein its entirety, may utilize a high frequency waveform. Embodiments ofRF generator circuits as described herein may be used to supply highfrequency waveforms to such ion modifiers. Additionally, embodiments ofRF generator circuits producing high frequency waveforms may be utilizedin various other applications.

Embodiments of RF generators including series resonant circuitsincluding a bifilar toroidal dual inductor as disclosed herein mayprovide high output voltage at high frequency (e.g., at least severalMHz). A bifilar toroidal dual inductor may provide a desired resonantfrequency, while having a small size and a low radiated magnetic field.Additionally, the stray capacitance between the windings of a bifilartoroidal dual inductor may provide self-resonance. Additionally, in oneembodiment a bifilar toroidal dual inductor does not require an air gap,provides close coupling, and is of simple construction. A toroidal coremay comprise any ring shape which need not be circular, for example itmay be square, ellipsoid, rectangular, or any other closed shape. In oneembodiment a toroidal core comprises a toroid shape.

While the active devices in each of the embodiments are illustrated asNMOS field effect transistors, in other embodiments other suitabletransistors (e.g., PMOS FET's, JFET's, BJT's, etc.) are used.Additionally, any other suitable active device, such as a voltagecontrolled impedance, may be used.

The feedback device and the diode disclosed with regard to the aboveembodiments, may be used in conjunction with any of the embodimentsdisclosed herein.

While the self-resonant dual inductor is illustrated as a bifilartoroidal dual inductor, in other embodiments, other suitable types ofself-resonant dual inductors are used.

In an embodiment there is provided an RF circuit for providing a radiofrequency signal, the circuit comprising: a dual inductor including onewinding including an input and an output, and another winding includingan input and an output; wherein the one winding and the another windingare arranged to provide, between the one winding and the anotherwinding, a parasitic capacitance selected to determine the frequency ofthe radio frequency signal; and wherein the outputs of the windings areconfigured to electrically couple to a capacitive load. The one windingand the another winding can be spatially arranged so the selectedparasitic capacitance and the inductance of the dual inductor provide aresonant circuit having an RF resonant frequency. For example theresonant frequency provided by the inductance of the dual inductor andthe selected parasitic capacitance may be at least 0.5 MHz, or at least1 MHz, or at least 3 MHz. In some of these possibilities the resonantfrequency provided by the inductance of the dual inductor and theselected parasitic capacitance may be less than 15 MHz, or less than 50MHz. The spatial arrangement of the windings may comprise selecting thelength of the windings, and the spacing between them and/or thedielectric constant of any coating on the winding. In an embodiment theRF circuit further comprises the capacitive load, and the selectedparasitic capacitance, and the capacitive load, and the inductance ofthe dual inductor cooperate to provide a resonant circuit having an RFresonant frequency. The capacitive load may comprise an ion modifier ofan ion mobility spectrometer.

The dual inductor may comprise a ferrite or iron powder core onto whichthe windings are wound. The core may be arranged in a closed loop shape,such as a toroid. In some embodiments, no core, or a non-magnetic coremay be used.

The drawings show capacitors 244, 246, in FIG. 2, 344, 346, in FIG. 3,and 444, 446 in FIG. 4. These capacitors are a representation of thedistributed capacitance between the windings of the dual inductor andany capacitance of a load coupled between the output of the windings.They are not intended to indicate actual capacitors. It will thereforebe appreciated that the representation in the drawings is merelyschematic, and most of the capacitance is actually between the outputsof the winding, rather than between each output and ground. In somepossibilities capacitors may be added at the positions indicated by 244,246, in FIG. 2, 344, 346, in FIG. 3, and 444, 446 in FIG. 4 in order totune the circuit.

In an embodiment there is provided an ion modification circuit for anion mobility spectrometer comprising: an ion modifier for subjectingions in a drift tube of an ion mobility spectrometer to a radiofrequency electric field; and a dual inductor including one windingincluding an input and an output, and another winding including an inputand an output; wherein the one winding and the another winding arearranged to provide, between the one winding and the another winding, aparasitic capacitance, and the outputs of the windings are coupled tothe ion modifier, wherein the parasitic capacitance of the dual inductoris selected based on the inductance of the dual inductor and thecapacitance of the ion modifier to provide a resonant circuit having anRF resonant frequency. In an embodiment the resonant frequency is atleast 3 MHz, and in some examples of this embodiment the resonantfrequency is less than 15 MHz. This resonant circuit may comprise thefeatures of any of the circuits described herein.

The ion modifier may comprise a first electrode, and a second electrode,wherein the electrodes are configured to be arranged across the drifttube for subjecting ions in the drift tube to a radio frequency electricfield between the electrodes.

In an embodiment the one winding and the another winding are arranged sothat an alternating current in the one winding induces an alternatingcurrent having opposing phase in the another winding.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) is to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

While reference is made to amplifiers and amplification elements, it isnot intended that an amplifier or an amplification element be limited toa single element. Instead, it is envisioned that these terms may in someembodiments encompass circuits including multiple elements, integratedcircuits, or any other arrangement suitable for amplification. The terms“stray capacitance” and “parasitic capacitance” are used interchangeablyherein to refer to an inherent capacitance associated with arrangingcharge carrying conductors in proximity to one another.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

Although the invention has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the invention defined in the appended claims is not necessarilylimited to the specific features or acts described. Rather, the specificfeatures and acts are disclosed as exemplary forms of implementing theclaimed invention.

What is claimed is:
 1. A circuit comprising: a dual inductor including a toroidal core, one winding on the toroidal core, the one winding including an input and an output, and another winding on the toroidal core, the another winding including an input and an output; one capacitor electrically coupled to the input of the one winding in parallel with the one winding; another capacitor electrically coupled to the input of the another winding in parallel with the another winding; wherein the outputs of the windings are configured to electrically couple to a capacitive load, wherein the dual inductor is configured to provide a voltage step up from the circuit inputs to the outputs of the windings, and wherein the dual inductor is configured to have current run in opposite directions through the windings of the dual inductor.
 2. The circuit of claim 1, further comprising: a capacitive load electrically coupled with the outputs of the windings of the dual inductor; wherein the circuit and the capacitive load form a resonant circuit.
 3. An RF generator circuit comprising: a power supply; an active device configured to output a signal; a dual inductor including a pair of windings wound on a toroidal core; and a capacitor electrically coupled with one of the windings of the dual inductor; wherein the power supply and the active device are electrically coupled with the capacitor and the one of the windings of the dual inductor; and wherein the dual inductor is configured to provide a voltage step up of the signal of the active device.
 4. The RF generator circuit of claim 3, wherein the power supply includes a DC power supply electrically coupled to a transformer producing two outputs, the outputs being out of phase with one another, the RF generator circuit further comprising: a second capacitor electrically coupled with the other of the windings of the dual inductor; wherein one of the outputs of the transformer is electrically coupled with the second capacitor and the other of the windings of the dual inductor.
 5. The RF generator circuit of claim 3 wherein the dual inductor is configured such that stray capacitance between the windings produces a self-resonance of the dual inductor.
 6. The RF generator of claim 3, wherein the other of the windings of the dual inductor is grounded.
 7. The RF generator of claim 3, further comprising: a feedback device configured to provide feedback from the dual inductor to the active device.
 8. The RF generator of claim 3, wherein the active device comprises: a transistor, the RF generator further comprising a diode coupled in series with the active device and the one of the windings of the dual inductor.
 9. The RF generator of claim 3, wherein the active device includes two transistors, with one of the transistors electrically coupled with one of the windings of the dual inductor and the other transistor electrically coupled with the other of the windings of the dual inductor.
 10. A method of generating a signal comprising: providing a drive signal to an active device; providing a power supply; providing a circuit including a bifilar toroidal dual inductor and a capacitor electrically coupled in parallel with at least one of the windings of the bifilar toroidal dual inductor, the active device and the power supply being electrically coupled to the circuit; and driving a capacitive load electrically coupled to the circuit in series with the bifilar toroidal dual inductor.
 11. The method of claim 10, further comprising: providing a feedback device providing feedback from the bifilar toroidal dual inductor to the active device.
 12. The method of claim 10, further comprising: providing the signal to an ion modifier.
 13. The method of claim 10, further comprising: driving the circuit at its resonant frequency. 